MIMO (Multiple Input Multiple Output) technology refers to the use of multiple antennas at both the transmitter and receiver to make full use of multipath components in space transmission and to use multiple data channels to send signals on the same frequency band, thereby linearly increasing channel capacity as the number of antennas increases. Such increase in the channel capacity consumes no additional bandwidth or additional transmit power. Therefore, it is an efficient means to increase the channel and system capacity.
In the MIMO technology, a base station node NodeB sends data to a user node UE over a physical HS-DSCH (High Speed Downlink Shared Channel), and sends control signaling and the like related to the HS-DSCH to the UE over an HS-SCCH (High Speed Shared Control Channel). The UE performs demodulation and decoding and the like on the data on the HS-DSCH by using control information carried on the HS-SCCH. Then, the UE generates ACK/NACK information according to the reception status over the HS-SCCH and based on whether the data on the HS-DSCH is decoded successfully. In addition, the UE also measures downlink channel status, generates CQI (channel quality indicator) information, selects a precoding matrix that allows a maximum channel capacity in a precoding matrix set of a precoding protocol, and generates a PCI (precoding control indication) according to a sequence number of the precoding matrix. The UE bears the ACK/NACK information, CQI information, and PCI information over an HS-DPCCH (uplink high-speed dedicated physical control channel) channel, and sends these information to the NodeB. The NodeB may use the CQI information fed back by the UE as a basis for service scheduling, perform precoding processing, according to the precoding matrix corresponding to the reported PCI, on the data to be sent, and select a corresponding transmit antenna according to a precoding processing result to send the data to the UE.
In an application of the MIMO technology, data transmission manners of a single stream and multiple streams are available. The single stream refers to that each transmit antenna sends the same data block, and the multiple streams refer to that each transmit antenna sends different data blocks. During data transmission, a base station switches between single stream and multiple streams according to actual situation about channel quality, thereby ensuring power requirements on the receiver. With regard to the single-stream transmission manner, because of location changes of the transmit antennas or channel quality, and the like, a big difference is caused between shadow attenuations experienced by the transmit antennas for sending data; or when antenna polarization directions are inconsistent, the receive power on the receiver may be extremely imbalanced, or an extreme scenario may exist, where the receiver can receive the power of only one transmit antenna. These may result in a probabilistic negative gain on the MIMO single stream compared with a conventional single-transmitting HSDPA (high speed downlink packet access), thereby affecting communication quality.